AB-INITIO CALCULATIONS OF THE ELECTRONIC-STRUCTURE OF THE WURTZITE COMPOUNDS CDS AND CDSE

We report ab initio calculations of the lattice constants and the electronic structure of the hexagonal wurtzite semiconductors CdS and CdSe. The calculations have been carried out self-consistently in he local-density approximation employing nonlocal, separable, and norm-conserving pseudopotentials. We use Cd12+ ionic pseudopotentials so that the Cd 4d electrons are explicitly taken into account as valence electrons. The calculated electronic structure is compared with photoemission data. calculated and measured bands show good agreement in the energy region of the mostly anion-derived s-p valence bands. The calculated Cd 4d bands result for both compounds roughly 3 eV too high in energy as compared to the measured data. This rigid shift of the narrow 4d bands is related to correlation effects which are not fully taken into account in the local-density approximation.